If your Coinbase account has been shut down due to violations of the user agreement, your remaining balance must be withdrawn from your account.
When you sign in, you will be prompted to withdraw all cryptocurrency from your account.
To withdraw cryptocurrency:
Obtain an external address from a third-party wallet provider and enter that address to withdraw the funds. Below are some options for obtaining an external cryptocurrency address:
Bitcoin: https://www.bitcoin.org/ (under "Getting started with Bitcoin," click the "Choose your wallet" link)
Note that Coinbase can no longer provide you with currency conversion services. To convert your cryptocurrency, you must use a third-party brokerage or exchange.
When you have successfully withdrawn all funds from your Coinbase account, you will be able to close your account.