The Constitution implicitly authorizes the federal government to seize private property (as well as life and liberty) by way of the Fifth Amendment. So, short answer, yes, but due process must (should) be afforded and, in the case of property, the seizure must serve a public purpose and be accompanied by just compensation.
Now, at the onset of the ACW, the Dred Scott Decision already explicitly held slaves to be property, subject to 5th Amendment protection for the owner, but what happened if the government convicted a slave of a crime and imprisoned them? Would they need to pay the slave owners?
This was answered in the negative by the DC Circuit in U.S. v. Amy in 1859. Frankly, this Decision performs some legal/logical gymnastics typical of the Taney-era courts, but ultimately holds that the slaves imprisonment is essentially incidental to his ownership, and, therefore, the government did not need to reimburse the slave owner for lost labor value. Here is the case, if curious:
https://law.resource.org/pub/us/case/reporter/F.Cas/0024.f.cas/0024.f.cas.0792.2.pdf
So, leading into the civil war, there was precedent of the Federal government seizing slave property without compensation, but let’s talk about contrabands in particular.
As far as I know, the term “contrabands“ originates from the Fort Monroe incident and General Benjamin Butler’s reaction. In May of ‘61, three slaves were leased to the Confederate government by their owner and put to work on rebel defenses. These slaves, understandably, weren’t thrilled with this and escaped to Union lines at Fort Monroe, VA. Shortly thereafter, their return was requested by a Confederate officer under flag of truce. Gen. Butler was an attorney, and knew that, under the prewar fugitive slave act, he was technically obligated to return them, but, as a trained attorney, he immediately began looking for a better interpretation of the law. His command eventually took the position that the slaves were part of the enemy war effort and therefore subject to confiscation as contraband.
He essentially made this up as a practical response to either technically violating traitors’ civil rights or giving them back a means to wage war on the United States.
While there is international precedent for a belligerent power to seize supplies and resources of another belligerent power (e.g. blockades), we must remember that the Lincoln Administration’s official position was that the South could not legally secede. Therefore, the could not be a “belligerent power,” because they were still technically subject solely to US jurisdiction. If this was true, rebels should still enjoy Constitutional protections. Therefore, Butler’s reasoning and the subsequent adaption by other Union commanders, notably Fremont, caused a degree of angst in Lincoln’s cabinet.
Congress, or what was left of it after most of the South packed up its toys and went home, gave post hoc approval of Butler’s actions with the Confiscation Act of 1861. Under that law, slaves were to be treated the same way as rifles, cannon, and other military supplies, in that, if they were used in support of the rebellion, they were forfeit. This, pragmatically makes sense, but what about legally?
During the war, I am not aware of the issue being raised. This doesn’t surprise me, because any Confederates wouldn’t recognize US Federal jurisdiction. Even if they tried to appear in court, they would probably have been arrested on the spot.
After the war, there were claims for “just compensation,” based in taking in the War. The most famous is US v. Lee in 1882, when Robert E. Lee’s family sued, and won, possession of Arlington National Cemetery (which they immediately sold back to the government).
As for human property, the Texas Supreme Court held in Hall v. Kesse (1868), that the taking of slaves without compensation violated the 5th Amendment; however, by that time, the Constitution was already amended to prohibit slavery.
Tying this all together, there was some precedent. Wartime expediency dictated some actions that could have been seen to violated the 5th amendment, but that conflict was resolved by passage of the 13th Amendment, which held that people were not actually property all along. Something I hope we can all get behind.
For a more in depth discussion, and my sources for much of this:
https://digitalcommons.lmunet.edu/cgi/viewcontent.cgi?article=1103&context=lmulrev