It looks like it is legal as long as no one is intending to fraud the other.I assume they are legal here. I used to have a loan with a bank which I payed with post dated checks. I will look into it, but I have never been questioned on it. I actually give the tenants a discount for it, making the rent $50 less if they provide post dated checks, which I guess means it is optional, though I have never had anyone opt to pay the higher rent.
The funny thing about checks now is that they are being used like debit cards by the stores. The check is scanned and the funds are taken directly out of the customers account. The check is often handed back to the customer and if there is insufficient funds, the sale is denied on the spot.