Employers are not allowed to place long-term of indefinite holds on employees' paychecks. In most states, there are laws in place regulating how long employers have to compensate employees after they have worked hours. Federal law also requires businesses to issue prompt payment for hours worked.
Withholding a paycheck is not the same as taking withholdings from paychecks. In general, when businesses refer to withholdings, they mean mandatory deductions taken out of an employee's wages to cover things such as taxes and insurance. These types of withholdings are legal and should be taken out of every paycheck the employee earns, including the first.