Well, there is no legal basis for FIFA or IOC to ban Russia and Belarus from international sports. In their charter, both organizations proclaim to be unpolitical, the said charter is signed by all members of not only both organizations but also members of FIBA, FIVB, etc.
Russia and Belarus will point directly to that charter, arguing that they have no influence over the politics of their countries, and politicians do not interfere in their countries' sporting matters, as imposed by the very same charter of these organizations.
They will also argue that countries like Kuwait, Eritrea, Malaysia were suspended because of politicians' influence on FA in their countries.
The TAS/CAS will find no legal ground for suspending Russia and Russian clubs by FIFA and UEFA because the Russian FA abides by the FIFA charter, whilst FIFA ignores it completely for P.R stunts.
FIFA might argue about human rights and how Russia violates H.R. in Ukraine, Russians will backfire by stating Guantanamo, Uighurs, Gilet Jaune, Inuit people, U.A.E, and Saudi Arabia in Yemen, Armenia/Azerbaijan conflict, Israeli/Palestinian conflict, etc. but more importantly how Paedophilia is so prevalent in many an FA across the globe, especially in Gabon, Haiti,
france, Mongolia, etc. and how FIFA keeps ignoring them or tries to make these cases disappear. Not only that, but also match-fixing in Eastern Europe, South America, Africa, Asia and how recently FIFA is unable to protect its employees, e.g. in Cyprus or
mexico where Mafia and Cartels control, extort, batter, and assault, etc.
Not only that but also human trafficking and children traficking from African countries into South East Asia, especially to Thailand to play football there.
FIFA has just shot itself in the foot, banning Russia, the decision will be turned in favor of Russia and Russian clubs, and no wonder if we see Zenit v RB in the next week
If you want to argue about IOC suspending Russian athletes, well that was a case of doping, which is tightly related to sports