If Mandal commission report recommends Jats into backward category, then there is a provision in the constitution to give them reservation:
Why Mandal Commission or NCBC is so important:
Neither the Constitution nor the law prescribes the procedure or method of identification of backward classes. Nor is it possible or advisable for the court to lay down any such procedure or method.
It must be left to the authority appointed to identify the backward classes. It can adopt such method/ procedure as it thinks convenient and so long as its survey covers the entire populace, no objection can be taken to it. Identification of the backward classes can certainly be done with reference to castes among, and along with, other occupational groups, classes and sections of people. One can start the process either with the occupational groups or with castes or with some other groups. Thus one can start the process with the castes, wherever they are found, apply the criteria (evolved for determining backwardness) and find out whether it satisfies the criteria. If it does-what emerges is a “backward class of citizens” within the meaning of and for the purpose of Article 16(4).
Similar process can be adopted in the case of other occupational group, communities and classes, so as to cover the entire populace. The central idea and overall objectives should be to consider all available groups, sections and group/ class encompassing and overwhelming majority of the country’s population, one can well begin with it and then go to other groups, sections and classes.
According to article 16(4).
Article 16(4) in The Constitution Of India 1949
(4) Nothing in this article shall prevent the State from making any provision for the reservation of appointments or posts in favor of any backward class of citizens which, in the opinion of the State, is not adequately represented in the services under the State
Further I would recommend you to read, Constitutional provision for reservation:
http://persmin.gov.in/otraining/UNDPProject/undp_modules/Reservation%20in%20Service.pdf
Hence its not wrong to say that Reservation is our constitutional right, if we have substantial evidence to prove that we fall into backward category!!