...I never knew it was "illegal", who says its illegal?
OSHA says...
Title: Logging Operations
Paragraph (h)(1)(ix) -- Domino Felling
The final rule prohibits domino felling. OSHA defined domino felling in the final rule as "[t]he partial cutting of `multiple trees' which are left standing and then `pushed over with a pusher tree'." In the preamble OSHA explained that domino felling was a method of attempting to fell a line or row of trees by partially cutting the trees and then pushing the end tree into the others, thereby creating a domino falling effect. (59 FR 51699, 51724). There was considerable evidence in the rulemaking record that such a method of felling a group of trees is extremely dangerous because there is greater likelihood the line of trees will not fall in the intended direction or may not fall completely, thereby creating even greater hazards (Ex. 5-42, 5-46; Tr. W2 231, OR 659). The hazards associated with domino felling are further increased where a danger tree is among the line or row of trees to be felled using this chain reaction method. Therefore, OSHA emphasized that danger trees also could not be felled using domino felling.
After publication, OSHA was requested to further clarify whether the felling of a single danger tree by felling another single tree into it is prohibited under the final rule. The final rule does not prohibit this practice in all cases, since the definition of domino felling in the final rule does not include the felling of a single tree with another tree. The domino felling that is prohibited in the final rule is the felling of multiple trees with a pusher tree. OSHA is revising the final rule to identify practices which are not considered to be domino felling, and therefore, are not prohibited by the standard.
However, the practice of felling a danger tree by felling another one into it, while it is not prohibited, is not automatically permitted to be used whenever a danger tree is felled. Paragraph (h)(1)(vii) of the final rule also requires that where a danger tree is felled or removed, the feller must use a technique that minimizes employee exposure to the hazard. In some cases, felling a danger tree by felling another tree into it will not minimize employee exposure to the hazards, and may even increase the risk the feller faces in removing the danger tree. As OSHA pointed out in the preamble, commenters told OSHA that felling a danger tree by felling another one into it is a safe technique when used by an experienced feller, but only "in certain situations" (Ex. 5-74 through 5-92). Other commenters told OSHA that this technique is generally not considered safe practice (Ex. 5-42, 5-46). In clarifying that this technique is not prohibited under the final rule, OSHA is permitting that a danger tree be felled in this manner only where a careful examination of mechanical techniques is first made and where it is also determined that the hazards felling the danger tree in this manner can be sufficiently minimized. The revised compliance directive notes that felling a danger tree by this method does not always minimize employee exposure to the hazard under paragraph (h)(1)(vii), and emphasizes that a safer method to remove a danger tree is to pull the tree down with a skidder or mechanical feller (Ex. 5-43).
Above from...
Logging Operations - 60:47022-47037
