This is not a Bitcoin Exchange where the founders have the freedom to do whatever they want.

I don't think you're allowed to limit withdrawals on savings accounts or checking accounts. (Beyond the 6x monthly limit on savings)

Money Market accounts are allowed to have limits (and haircuts) applied. Etc. etc. As a bank, they'd have different accounts with different rules on each kind of account. But Money Markets aren't allowed to be mixed with the long-term treasuries that SVB were holding.

So it really depends on the mix of accounts, various regulations and such.

My understanding is this isn't a "run on the bank" situation, they were too successful growing their deposit book and couldn't grow their loan assets fast enough to keep pace. So they bought a lot of MBS so they at least were earning some yield with which to pay interest on their deposit liabilities but took heavy losses when rates moved against them so were inadequately capitalised. They tried to raise additional capital and a couple of key miscommunications in that process really spooked the market and they suddenly collapsed.

They could have limited withdrawals before it started, but not after. Banks used to offer savings accounts, where the bank could impose a delay on withdrawals. That delay was once 30-60 days, then 7 days, and now it's mostly gone. This allowed small banks time to sell off some assets in the event of a sudden increase in withdrawals. In exchange for that, savings accounts paid higher interest. This was part of the dull and boring banking system designed in the 1930s.

See "Savings and Loan Crisis" for how that ended.[1]

[1] https://en.wikipedia.org/wiki/Savings_and_loan_crisis

No. A bank that refuses a demand on a demand deposit account is by definition in default.

I'm sure a bank limiting withdraws would have made matters even worse.

Federal law

They could not change the terms on accounts, no.