I remembered the 1967 Outer Space Treaty as preventing militarisation of space. It turns out, not wholly. Celestial bodies (the moon, asteroids, etc) are out of bounds completely and are only for 'peaceful purposes'. For space itself, the ban is on WMDs, like nuclear weapons, in space anywhere.[0]

But the US has maintained a polite fiction that space is not weaponised/militarised. This is a break from that. The wording[1],

> The United States now has on-orbit space control weapons capable of defending the joint force against hostile adversary action.

is stated as 'That phrase was very well thought out.'. It looks like they're positioning it as purely defensive.

Which is allowed but being open about it legitimises the concept of weapons in space. It's worrying, and potentially destabilising. I expect they mean it as a deterrent but I frankly this it's irresponsible in that it invites an open presence from other countries too.

[0]: You can download a PDF here: https://treaties.un.org/Pages/showDetails.aspx?objid=0800000... and the relevant section is Article IV.

[1] https://aviationweek.com/defense/missile-defense-weapons/us-...

(I can't read the FT link, paywall, but the FT is not a great source these days anyway.)