Law enforcement in embassies
<p><a href="https://law.stackexchange.com/a/79832/36903">This answer</a> tells us that embassy soil is inviolable, as per Vienna Convention on diplomatic Relations 1961, art. 22. That means the host country ('s law enforcement) cannot enter the premises nor do anything inside.</p>
<ol>
<li><p>I assume that applies only without the consent of the head of the diplomatic mission, but is that right? My understanding of the arrest of Julian Assange in UK by bobbies given access by the Ecuador diplomats seems to go that way.</p>
</li>
<li><p>What about the mission country's law enforcement? In the Agent 47 movie, US Marines make an arrest just in front of the building of the US embassy in Germany, so that seems like the mission country does have law enforcement power within the embassy grounds, but some other source than that not-so-realistic movie would be appreciated.</p>
</li>
<li><p>Assuming point 2 is correct, and a suspect is arrested, what happens next? If the suspect were to be moved to the mission country's sovereign soil (which the embassy is not), would that country's laws allow them to be prosecuted, or would the court consider the act they committed to have been done in foreign sovereign territory ?</p>
</li>
<li><p>Still assuming point 2 is correct, what would be the conditions for moving the suspect from the embassy (within the host country) to the mission country? can the host country forbid it?</p>
</li>
<li><p>Finally, what happens if, say, a hostage-taking attack prevents anyone from the embassy to communicate the permission given in point 1, and the law enforcement capacities from point 2 (from the mission country) are not capable of responding (because they are incapacitated for example)?
The most extreme legal response would be for the host country to revoke diplomatic credentials for the diplomatic mission, and to invade it with its own law enforcement after a given period of time. Is there another way? For example, can a mission-country diplomat (the minister for foreign affairs for example) provide a point-1 authorization from abroad, without consent from the ambassador? Can the mission country send troops to the embassy through the host country? Can the host country &quot;lend&quot; troops to the mission country's command?</p>
</li>
</ol>

<blockquote>
<ol>
<li>I assume that applies only without the consent of the head of the diplomatic mission, but is that right?</li>
</ol>
</blockquote>
<p>Yes.  The Vienna Convention on Diplomatic Relations is quite clear on that.  Article 22(1) (emphasis added):</p>
<blockquote>
<p>The premises of the mission shall be inviolable. The agents of the receiving State may not enter
them, <em>except with the consent of the head of the mission.</em></p>
</blockquote>
<blockquote>
<ol start="2">
<li>What about the mission country's law enforcement?</li>
</ol>
</blockquote>
<p>Agents of the sending state can do pretty much whatever the sending state wants when they are on the premises of the mission (including <a href="https://en.wikipedia.org/wiki/Assassination_of_Jamal_Khashoggi" rel="nofollow noreferrer">murder</a>), and even to some extent outside the premises of the mission, because they have personal immunity.  Such an arrest could lead to a diplomatic incident, though, so they have to behave responsibly.  The status of such an arrest in the law of the receiving state is not regulated by the convention and probably varies depending on the local law and perhaps bilateral agreements.</p>
<blockquote>
<ol start="3">
<li>Assuming point 2 is correct, and a suspect is arrested, what happens next? If the suspect were to be moved to the mission country's sovereign soil (which the embassy is not), would that country's laws allow them to be prosecuted, or would the court consider the act they committed to have been done in foreign sovereign territory?</li>
</ol>
</blockquote>
<p>That depends on the law of the country in question.  Many countries assert at least some extraterritorial jurisdiction (over their foreign missions and otherwise), so a court could claim jurisdiction over a crime even if it was committed in foreign territory.</p>
<blockquote>
<ol start="4">
<li>Still assuming point 2 is correct, what would be the conditions for moving the suspect from the embassy (within the host country) to the mission country? can the host country forbid it?</li>
</ol>
</blockquote>
<p>Yes.  The host country retains control over its territory, including its airspace.  There have been attempts to smuggle people in the diplomatic &quot;bag,&quot; but this is an abuse of the convention, which provides that the diplomatic bag &quot;may contain only diplomatic documents or articles intended for official use.&quot;</p>
<blockquote>
<p>Finally, what happens if, say, a hostage-taking attack prevents anyone from the embassy to communicate the permission given in point 1, and the law enforcement capacities from point 2 (from the mission country) are not capable of responding (because they are incapacitated for example)? The most extreme legal response would be for the host country to revoke diplomatic credentials for the diplomatic mission, and to invade it with its own law enforcement after a given period of time. Is there another way?</p>
</blockquote>
<p>The sending country's foreign minister can give permission to the receiving country to enter the premises.  You can't just revoke the diplomatic credentials and have immediate access, because that would allow regular end-runs around the immunity provisions (Article 45).</p>
<blockquote>
<p>For example, can a mission-country diplomat (the minister for foreign affairs for example) provide a point-1 authorization from abroad, without consent from the ambassador?</p>
</blockquote>
<p>The convention doesn't seem to say this explicitly, but since the foreign minister is the ambassador's boss, yes.</p>
<blockquote>
<p>Can the mission country send troops to the embassy through the host country?</p>
</blockquote>
<p>Only if the receiving country allows it.</p>
<blockquote>
<p>Can the host country &quot;lend&quot; troops to the mission country's command?</p>
</blockquote>
<p>By mutual consent, yes, though it would more likely be some sort of joint operation whereby both countries would have to agree on the orders being given.</p>

diplomatic-immunity