Not all regulations in the Holy Law can be observed nowadays. 

A lot of regulations were only possible to observe in a time when People of Israel had their own kingdom and when they lived in the Holy Land Beeretz Yisrael uvizeman hamalkhut בְּאֶרֶץ יִשְׂרָאֵל וּבִזְמַן הַמַּלְכוּת, such as: 

Tithes Maaser מַעֲשֵׂר the tenth of the all agricultural yields, which were given each year to the tribe of Levi and every three years a tenth of all agricultural yields donated were donated to Levites, newcomers, orphans and widows. 

The Sabbatical year Shmita שְׁמִטָּה was every seventh year, all debts were forgiven for limited time, slaves were released; the fields were not sown and cultivated and lied fallow. 

Jubilee Yovel יוֹבֵל after seven sabbatical years Sheva shemitot שֶׁבַע שְׁמִטּוֹת, each fiftieth year all properties were given back to their original owners or their heirs; the fields were not sown and cultivated and all slaves were released. 

The above mentioned (and similar) regulations are not obligatory at this present time. A lot of criminal and civil laws exist that can’t be applied today, because  we are subordinated to the laws of the countries in which we live. Other laws and rites are eternal חֻקֹּת‏ עוֹלָם Khukot olam such as: circumcision Milah מִילָה, holidays, purity and moral laws, these can never expire or lose sense; they remain obligatory forever and in every place where we live.