Either the 1040 or the 1040A tax forms can be used to file separate returns, regardless of community property issues. The 1040-EZ form cannot be used to file married-filing-separately.
Generally, form 1040A is used by taxpayers claiming the standard deduction, with form 1040 being used by taxpayers claiming itemized deductions. The trick with separate returns, whether or not community property is at issue, is that if one spouse itemizes deductions, the other must also itemize. It is a good idea to settle this before filing. Otherwise, one of you may receive a notice from the Internal Revenue Service requiring an amended return.