Then again, according to the Supreme Court, even forced, unpaid road duty (chain gangs anyone?) is an inherent power of the government, so maybe this is ok.
> In view of ancient usage and the unanimity of judicial opinion, it must be taken as settled that, unless restrained by some constitutional limitation, a state has inherent power to require every able-bodied man within its jurisdiction to labor for a reasonable time on public roads near his residence without direct compensation.
https://supreme.justia.com/cases/federal/us/240/328/
(spoiler alert: according to the ruling, the US Constitution, including Amendments, does not limit this power; and this is in fact cited as justification for upholding the draft)