I think the well-tried legal cliché "notwithstanding" may offer a reasonable way of expressing this. After all, "óbice" means obstacle or impediment, and "X no ha sido óbice para que Y sea Z" means "X has not prevented Y from being Z", or in other words, "despite (or notwithstanding) X, Y has been Z". I don't think "prevent" works so well here.

As far as I can see, the tense must be perfect -- this is apparently referring to what has happened in the cases the TC has heard -- and "mínima" must mean "minimal": at the lowest end of the range of options available.

However, I must confess I find a couple of details confusing. First, I am not entirely sure of the sense of "su tutela": does "su" mean "del TC" or "del derecho"; is it the protection afforded (or awarded) by the court or the protection of the rights involved? I think it is probably the latter, but I don't really know. In practice it amounts to the same thing, and I have evaded the precise sense of "su" by simply omitting it and saying "the protection afforded".

However, I am still unclear about what they mean by "esto". Does it mean the fact that the TC has heard about 30 cases? I can't see what is being contrasted, and what precisely it is that has not prevented the "tutela" from being minimal. I'm probably being obtuse. At any rate, I feel that this translation renders what the text says with reasonable accuracy.

By the way, I also find "promedio" odd, and suspect that it just means "approximately". I can't see what 30 could be an average of; does it mean 30 cases per year? I don't know.