The law referred to is those laws which apply to the descendants of Noach. These laws were also restated at the giving of the Torah at Sinai.
Proper understanding of what those laws are and how every individual can best cleave to the Creator of us all is transmitted to the nations by Israel.
This is in keeping with the idea of being a light to the nations.
And this is the very essence of the second paragraph of the Aleinu prayer said at the close of each of the daily prayer services which is attributed to Yehoshuah (Joshua).
We therefore put our hope in You, L-rd our G-d, to soon behold the glory of Your might in banishing idolatry from the earth, and the false gods will be utterly exterminated to perfect the world as the kingdom of Shadai. And all mankind will invoke Your Name, to return to You, all the wicked of the earth. They will realize and know, all the inhabitants of the world, that to You, every knee must bend, every tongue must swear [allegiance to You]. Before You, L-rd, our G-d, they will bow and prostrate themselves, and to the glory of Your Name give honor. And they will all accept [upon themselves] the yoke of Your Kingship, and You will reign over them, soon, forever and ever. For the Kingship is Yours, and to all eternity You will reign in glory, as it is written in Your Torah: the L-rd will reign forever and ever. And it is said: And the L-rd will be King over the whole earth; on that day the L-rd will be One and His Name One.
That we look with hope to You, L-rd, our G-d, to soon see, through the culmination of Torah study and prayer (בתפארת), Your brilliance (עזך); to remove the confusion of inappropriate adulation (גלולים) from the earth. And those heroes/icons (והאלילים) will be absolutely divested. To harmonize the world (לתקן עולם) in relation to the paramount priority of the continuation and propagation of life (במלכות שדי).