There never was a law stating the chains needed to be one way or the other, as long as they're short enough to keep the tongue from touching the ground should it become detached. In most cases it's easiest to cross them but you can use any method you like. See (d).
5. (1) A full trailer shall be coupled to the frame or an extension of the frame of a truck tractor or trailer with a safety connecting device that will prevent the full trailer from breaking loose in the event the tow bar fails or becomes disconnected. R.R.O. 1990, Reg. 618, s.5 (1).
(2) The safety connecting device referred to in subsection (1) shall,
(a) not be attached to any part of a trailer hitch that would render the safety connecting device ineffective should the trailer hitch or its attachment to the towing structure fail;
(b) have the minimum slack necessary for adequate articulation;
(c) have an ultimate strength not less than the gross weight of the trailer or trailers being towed and where the safety connecting device consists of two chains, two cables or two other links, each chain, cable or other link and its attachments shall have an ultimate strength equal to the gross weight of the trailer or trailers being towed;
(d) be connected in such a manner so as to prevent the tow bar from dropping to the ground, and to keep the swing of the full trailer within safe limits in the event the tow bar fails or becomes disconnected;
(e) be equipped with a hook or hooks or other means of attachment that will not become disconnected accidentally;
(f) where it is used in conjunction with a hinged tow bar and where the safety connecting device consists of two chains, two cables or two other links, be attached to the forward axle or chassis frame of the forward axle of the full trailer at two points as far apart as the configuration of the axle or frame permits and equidistant from the centreline of the full trailer;
http://www.ontario.ca/laws/regulation/900618