NC posted the entire bill here. It contains several clauses, one of which authorizes the president to suspend the writ, two provide indemnity against prosecution for prior acts. I don't know whether or not that implies the congress knew they could not retroactively authorize his actions or not. Maybe it's just thier way of insuring all bases are covered to preempt judicial review.
16. The habeas corpus can be suspended only by authority of the legislature. The constitution of the United States provides, that the privilege of the writ of habeas corpus shall not be suspended unless when, in cases of invasion and rebellion, the public safety may require it. Whether this writ ought to be suspended depends on political considerations, of which the legislature, is to decide. 4 Cranch, 101. The proclamation of a military chief, declaring martial law, cannot, therefore, suspend the operation of the law. 1 Harr. Cond. Rep. Lo. 157, 159 3 Mart. Lo. R. 531.