They could not alter the eventual shifts in production that owe to enormous changes in relative prices across the economy. Protectionism might enable a worker in a declining industry to hold onto his job longer.
But would it not be better for that worker to seek a new career in a more viable industry at age 35 than to hang on until age 50, when alternative job opportunities would be far scarcer and when the lifetime benefits of additional education and training would be necessarily smaller?