straightlaced (adj.)

• dour
• firm
• fundamentalist
• hard
• hidebound
• inexorable
• inflexible
• iron
• ironclad
• muscle-bound
• obdurate
• obstinate
• orthodox
• procrustean
• puritanic
• relentless
• rigid
• rigorous
• rockbound
• stiff
• straitlaced
• stubborn
• unbending
• uncompromising
• unrelenting
• unyielding