Passed by Congress in January 2019 and signed by Trump. " Employees furloughed as a result of a lapse in appropriations shall be compensated for the period of the lapse on the earliest date possible after the lapse ends, regardless of scheduled pay dates. "
* excepted (essential) employees (including ATCs) are required to work, are not getting paid, but will be paid back for their work when Congress passes a new appropriations bill
* furloughed (non-essential) employees are told not to work, are not getting paid, but will be paid back under GEFTA once the shutdown ends, without any new law.
To be clear, I'm trying to state the facts, not my opinions.