None of which say anything about planetary contamination. GP is right that there is absolutely no laws enforcing “planetary protection” on commercial entities (thankfully).
UNOOSA, Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, Art. IX [1]:
"States Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination..."
Note that State parties are responsible for the actions of their nationals later in the paragraph.
Is the above wrong? I admit to not being a space person.
Edit: [1] http://www.unoosa.org/pdf/publications/STSPACE11E.pdf
“States Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter....”
The “their harmful contamination” part clearly refers to something plural (the moon and other celestial bodies). The second part would be redundant if those were sources, rather than recipients of contaimination.
"State Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose."