There are recent proposals for an exit tax on high-income residents who leave California. For details see:
If enacted, California would follow in the footsteps of the old Soviet Union and East Germany in taxing people who leave the state.
Would a tax like this violate the US Constitution based on interstate commerce?
There is nothing in the US Constitution that specifically addresses the rights Americans to freely move from one state to another. My understanding is that right was spelled out in the Articles of Confederation, but was not included in the US Constitution explicitly. Would the right of freedom of movement be covered under the 9th or 10th amendments?
Stock here---you can look at the Articles of Confederation, and Constitution here
The AoC states pretty clearly, free to move around among States.
The better to secure and perpetuate mutual friendship and intercourse among the people of the different States in this Union, the free inhabitants of each of these States, paupers, vagabonds, and fugitives from justice excepted, shall be entitled to all privileges and immunities of free citizens in the several States; and the people of each State shall free ingress and regress to and from any other State, and shall enjoy therein all the privileges of trade and commerce, subject to the same duties, impositions, and restrictions as the inhabitants thereof respectively, provided that such restrictions shall not extend so far as to prevent the removal of property imported into any State, to any other State, of which the owner is an inhabitant; provided also that no imposition, duties or restriction shall be laid by any State, on the property of the United States, or either of them.