It adopted a policy of isolationism
The framers of the Constitution devised a system wherein no one branch of the Government would be able to dominate.
This means that, by design, each branch of the US Federal system is co-equal.
This ensures that before action is done on behalf of the people of the US by the Federal government, there are adequate safeguards to ensure that what is being done is done within the bounds of the Constitution.
I believe the answer is, To pay the fine and go to jail.
Explanation:
Theodore Parker was an abolitionist, meaning he was against slavery. I think that he would stand by his beliefs and go to jail, rather than move to Canada, or support slavery.