There was this case.

I haven't reread the article but it's from over a decade ago. Man sued a bank and won but they ignored him until he began foreclosure proceedings on a branch office.

I work in tech, but for a financial company so what I’ve gathered is from required compliance training.

Large financial institutions are obligated to block and report attempted transactions on blocked accounts. That would likely include blocks on trading accounts I imagine.

As far as actually seizing it, I don’t have solid info but in a mostly digital finance world it probably just involves transferring access and ownership controls to a government entity (by the institutions).

Hope that helps

In the USA, government agencies like the IRS and FBI can order banks and other financial institutions (like brokers) to freeze your accounts so that you can't access the money. Under RICO, they can also take possession of your stuff like vehicles and such. They just show up with guns and badges and take it.

This is why some wealthy people squirrel money away in "numbered Swiss Bank accounts" that are outside US jurisdiction and much harder to identify who owns what. However, the international laws have changed over time and I believe it's far less convenient than it used to be.

The wealthy can always find a way to hide their money. Some are better at it than others.

A lot of them have legal insurance, too. For example, Theranos scumbag Elizabeth Holmes went bankrupt, but insurance pays for her exorbitant legal expenses.

Varies state by state, there is no one universal rule.

Some states require a conviction, some don't.