1. This brings up the question of being able to agree to a contract before the contract is written which makes no sense.
2. If it's legal then why don't all companies do it. Instead, companies like Google regularly put out updated terms of service which you have to agree to before continuing to use their service. Often times you don't realize it because it's just another checkbox or button to click before signing in.
Imagine if a landlord sued a tenant after 1 year for a new roof of an apartment because the contract stated that "tenant will be responsible for all repairs" but the tenant pointed out that the contract also said "the house is in perfect and new condition".
Both things cannot be true, so the judge throws it out.
Same thing here, you can't grant someone a license to use something and then immediately say, "You can't use this without checking with us first" it is contradictory.