First of all a number of founding documents of the European Union and the Canadian Constitution recognize both the right to establish unions and the right to collective bargaining. What other civilized nations think and do when they express moral values superior to our own, establishes the inferiority of our values. The United States' history regarding the civil rights of non-whites, underscores that just because we do not now see a right as a part of the law, does not make our action morally correct nor our morality superior.
In terms of domestic law, Congress has sighed on to some of the international agreements regarding labor rights, and as such these have, all be it limited, legal standing.
http://law.onecle.com/constitution/article-2/25-domestic-obligations-of-executive-agreements.html On 19 June 1934, the US Congress passed a joint resolution authorizing the President to join ILO. On 20 August 1934, the US government and took its seat at the ILO. A number of ratified treaties may lend wight to the argument that the right to collective bargaining is an international convention. http://www.law.uiuc.edu/publications/cllpj/archive/vol_25/issue_2/MartinArticle25-2.pdf International Covenant on Civil and Political Rights Signed by The United States 5 Oct 1977 Ratified by The United States 8 Jun 1992 "Article 22 1. Everyone shall have the right to freedom of association with others, including the right to form and join trade unions for the protection of his interests. 2. No restrictions may be placed on the exercise of this right other than those which are prescribed by law and which are necessary in a democratic society in the interests of national security or public safety, public order (ordre public), the protection of public health or morals or the protection of the rights and freedoms of others. This article shall not prevent the imposition of lawful restrictions on members of the armed forces and of the police in their exercise of this right. 3. Nothing in this article shall authorize States Parties to the International Labour Organisation Convention of 1948 concerning Freedom of Association and Protection of the Right to Organize to take legislative measures which would prejudice, or to apply the law in such a manner as to prejudice, the guarantees provided for in that Convention." US reservation are here: http://www1.umn.edu/humanrts/usdocs/civilres.html
People who make profit through exploitation, always find a way to rationalize their injustice.