Checking Account?
I am no lawyer, but I do know Finance/Banking, this may be able to help...
But first, just to be clear, You have money in a checking account, one that is not restricted in any way (such as a CD or money market account may be) and they wont give you your money? Are they a small bank? The whole point of having a checking account and getting paid little or no interest on that money is that the cash should be available to you whenever banking hours are open. If you wanted a delayed withdrawl you could have your money earning much better interest then what they are offering.
First, make sure they are FDIC insured (Check on the window for the FDIC symbol. If it is a large bank, there is no doubt they are. If it is a small one, its not quite as definite). If they are, explain to them that what they are doing is not within the guidelines of the FDIC, and if they do not give you your cash immediately, you have no choice but to believe they dont have the cash available, thus in violation of strict FDIC rules and regs. If they still refuse, tell them you will be filing a complaint with the FDIC and they risk having severe fines and/or the FDIC insurance priveledge revoked.
As a word of caution, the only time I have heard of a bank not allowing you access to your checking account funds is when there is a federal sieze on the funds. Before you do any of this, be sure there is no legal reason they could be holding your cash (such as IRS violations, FBI suspicions on where you grew the cash, back child support, etc.). If the fed believes you are in something dirty, and if they have some level of proof, they can put a freeze on your cash. If you are sure none of this is the case, you should walk into the bank very upset, stating what I said. If they still refuse, (and you are SURE the fed isnt involved) contact the FDIC, a local news station and a lawyer. They should change their tune...
Good Luck.
D