Even without your signature agreeing to the rules and regulations, you are bound by them. The act of going to the academy shows consent to the academy's rules. What the signature does is provide evidence of your receipt of the rules. IF the reason you were dismissed was particularly "technical" and not something which would obviously be wrong (e.g. violation of a dress code; having an alcoholic beverage offsite and on your own time), then if you were never made aware of the rule and can persuasively or credibly show you were not aware, you may be able to legally challenge the dismissal. But if you were in fact aware of the rule, or it was something any reasonable person would know you should not have done (e.g. being drunk at or bringing alcohol to the academyh; using a CDS anywhere; posting racist comments on social media or engaging in sexual hassment; etc.) then you clearly could be dismissed for that reason.